1. Field of the Invention
The invention relates to an apparatus for catheter ablation in general and for radiofrequency catheter ablation of preferably living endomyocardial tissue in particular, and also to a corresponding ablation catheter and a process for its operation.
2. Discussion of Relevant Art
In the treatment of cardiac arrhythmias which are produced by electrically autonomous tissue and in particular by tissue which is not subject to the central excitation control of the heart, thermal coagulation of the tissue concerned has been shown to be successful, and is well-established in the field. In this procedure, the ablation catheter is pushed endocardially into the heart, and energy is delivered to the concerned tissue from an electrode at the tip of the catheter or from electrodes arranged along the longitudinal axis of the catheter, so that a local coagulation takes place and the tissue region causing the disturbed functioning is electrically isolated. In this procedure, the energy is usually delivered continuously to the electrode by means of a high frequency generator at frequencies of 300-700 kHz, and a coagulation scar is thus produced to a depth of 3-5 mm.
However, it is disadvantageous for this process that the temperature of some portions of the catheter is so high that blood coagulates and adheres to the catheter. Further ablation is thereby hindered, and cleaning of the electrode is necessary. The subsequent withdrawal and reinsertion of the catheter represents an additional stress for both the patient and the surgeon. Furthermore, there is great danger of thrombosis due to the coagulated blood. On the other hand, there is a requirement to further increase the energy delivered to the tissue, in order to reach, with greater depths of lesion, arrhythmogenic tissue regions which lie deep in the myocardium.